Let's see: we now have lost the first member of Trump's inner circle for clear, improper contacts with the Russians. We've discovered that Trump thinks its alright to have meetings around global security in a country club dining room, with open access to guests to take phone pics and even selfies with the nuclear football and its carrier photographed and ID'd. Finally, there is the apparent issue that no one really vetted the workforce at Mar a Lago, so presumably the largely foreign born workforce(per prior disclosures, lots of temp visas there) can accesss the President and world leaders unfettered.

Given the scale, and the fact that Benghazi and email scandals seem sort of bland and routine comparatively, how long does the Trump administration even last?

I can see Trump and a few of his sycophant yes-men getting kicked to the curb. But the entire administration? I doubt it.
Pence may very well end up POTUS.
Bannon may survive the purge. He's a shifty, shadowy kind of guy. Hell, he may even be POTUS right now. But I doubt Pence will put up with Bannon's bullshit.

NYT is reporting tonight that they have information of repeated contacts going back a year or so between numerous Trump campaign officials and associates with Russian intelligence agents. That would mean Pence had to know at some point. So, yes, the whole mess could come crashing down, with God-knows-what collateral damage.

I think it depends on whether you mean an actual removal of Trump or an effective end of his influence. Unless some smoking gun, a la Watergate, is revealed, I doubt he'll ever be impeached. I think he's looking at a bloodbath in the midterms. Which gets to the second point...the GOP is pleased with Trump. He makes erratic and ignorant statements, but in practice, he is doing precisely what they want a conservative president to do. I believe, if the erraticism continues, they will leave the political sweetspot and Congress will turn on Trump. I suspect will be a full 12 months

it must be frustrating, to be honest, for the GOP. They still never got their collective act together around what to do about ACTUALLY repealing the ACA, and the Trump debacle precludes them from getting any traction on any real agenda. Oh, and I think there will be smoking guns aplenty in under 4 weeks.

I concur, to an extent. At this point, Ryan and McConnell appear to be pleased, and thus, I see little to no resistance. However, I see no legislation reaching the floor or Mr. Trump's desk either. Obviously, they are pleased with the Gorsuch appointment. I'm interested to know why you think there will be a smoking gun. We can speculate. I'm really hoping that the transcript of the Flynn discussions is made public as I want to draw my own opinion as to who was directing him or whether he was "rogue."

multiple reports over the last week indicate that European security agencies, nervous about the bromance between the Trump camp and the Russians, were doing surveillance too, and dumping transcripts and other information on American press outlets. Couple that with the fact the US security agencies, having been dismissed and threatened by the Trump crew are searching for such a smoking gun hard, and as I say, I give it a matter of a few weeks.